The present invention relates to security systems and in particular is concerned with security systems which monitor a plurality of conditions including unauthorized intrusions into a protected area.
Security systems which provide coded signals from a plurality of remote sending units and decode the signals in order to produce an appropriate alarm are known in the art. In some of the prior art systems, such as disclosed in U.S. Pat. No. 2,899,674, the signals from the sending units are coded in order to identify the location from which the coded alarm signal has been sent. More recently, however, electronic security systems such as described in U.S. Pat. No. 3,833,895 are provided with transmitters that send signals coded or modulated in accordance with a particular condition that exists at a remote site. For example, a security system may include transmitters that are energized by motion detectors and perimeter switches actuated during unauthorized entry, by fire or gas detectors and other monitoring devices and by manually actuated emergency switches. When the transmitters send signals that are coded in accordance with a particular emergency condition, the central alarm station can decode the signals to determine exactly what condition exists and what action must be taken in order to counteract or address the condition.
In security systems which provide intrusion protection, it is desirable to provide a test mode of operation for determining that the intrusion sensors or switches and the associated transmitters are properly set and operative when the system is first turned on. When a test is conducted it is also desirable to disable the warning alarm generator so that personnel in the area or at remote monitoring stations are not prompted to respond to a false alarm.
Where high priority alarm signals such as those indicating fire or other emergency conditions are produced in the same security system that includes intrusion sensors, it is undesirable to permit a test mode of operation to disable a common alarm generator because the priority alarm signals would then be interrupted also. On the other hand, it is desirable to provide a testing mode of operation for the intrusion sensors even though a system may include other types of emergency sensors.
In security systems that are responsive to coded signals, it is known, for example from U.S. Pat. No. 3,795,896, to include portable sending units that can be employed from remote areas to disable the system before an authorized entry through a predetermined perimeter is to be made. But if the system includes sending units which monitor fire and other emergency conditions, the portable transmitter could disable other units that rely upon the same alarm generator.
It is accordingly a general object of the present invention to provide a security system which receives coded signals from a plurality of sensors including intrusion sensors, and which has a testing capability that does not interfere with priority alarm signals when proper functioning of the intrusion sensors is being examined. It is a further object of the invention to include in such coded security system a disarming function that does not interfere with priority alarm signals when intrusion signals are interrupted.
It is still a further object of the invention to provide a vehicle security system that allows an intrusion signal to be cancelled by an authorized person without totally disabling system responses to other sensors.